Mechanical, electrical and passive devices and techniques have been known and used for many years to modulate the output of lasers. Common mechanical techniques include the use of in-cavity choppers, rotating mirrors, prisms and the like. Kerr cells, Pockel's cells, and acousto-optical devices have been used to electrically control laser output characteristics. Bleachable dyes and other nonlinear elements have functioned as passive means for output modulation of lasers.
Also of recent interest are optical switches wherein laser output beams of desired power can be terminated by means of selectable gas pressures contained within a chamber through which the beam is focused; U.S. Pat. No. 3,433,555. Beams of collimated light have been caused to reflect within a transparent member by passage through slots formed therein of a fluid having an index of refraction less than the transparent material. Thus, by proper selection of the fluid and slots, the reflections can be controlled to position the output of the beam from the material; U.S. Pat. No. 3,537,643. Other devices of interest include those described in U.S. Pat. Nos. 3,121,169 and 3,625,593. The latter patent is of particular interest in that a means for the electrical control of light polarization is disclosed comprising in the path of a polarized light beam, a transparent container in which at least two optically active fluids are provided for rotating the plane of polarized light.
It is an object of the present invention to provide a means for modulating the output of a laser by means less susceptible to damage and thus capable of controlling high power output than state of the art devices. A further object of the invention is to provide a means for modulating a laser output which is more versatile and controllable than passive systems and much simpler and cheaper than electrical systems.